Tracking Covid-19 with Phones

Exploring the benefits and dangers of phone data being used for health security.

You may have read or seen how mobile phones have been used to track people from a single event to places all over the world. The maps demonstrate the real time potential spread of the Covid-19 virus. Every phone displayed as a moving dot on the map represents a unique person who may or may not have the virus. It’s amazing yet scary technology.

What’s the magic behind these maps?

Every mobile phone connected to a telephone network broadcasts a unique identifier. It lets you walk or drive down a road and keep talking on the phone: your unique identifier is attached to your phone connection and passed along from the nearest telephone tower to the next nearest telephone tower. These identifiers are hard-wired and cannot be changed.

The maps use phone identifier data from X-Mode and mapping software provided by Tectonix. Maps are published on social media to demonstrate their technologies and advertise to get business from academic researchers and others.

Of course, there are ways to hide a mobile phone. You can put a phone in airplane mode and turn off the setting that broadcasts your location data. But most people use their phone to talk with family and friends, as well as connect to the internet to check weather and do many different things. Most phones are always on and connected.

Maps that display people as they leave a single event claim to use only the unique identifiers for each phone which, in turn, are not easily tied to an individual name. The companies that create these maps claim their data is completely anonymous, which is true but in a limited way.

The New York Times and others have demonstrated that it is fairly easy to link a unique phone identifier to an individual. We live in one place, for example, so an identifier that stays overnight in the same location day after day likely represents the person who lives at that location. Where a person works also can be determined. And unique identifiers can be combined to identify family and friends.

These Covid-19 maps demonstrate how technology that is very useful — our phones — has serious positives and negatives that need to be known and debated. The collection of unique phone identifiers, for example, is mostly controlled by private companies like X-Mode with little or no government regulation. The companies use this data to create their maps of people leaving events. And still others, like the New York Times, use the unique identifier data plus other data to identify people who own specific phones.

People who don’t have phones present another interesting issue. They can’t be tracked, if tracking is useful.

Perhaps the most interesting question is what will happen after Covid-19 is no longer a public health problem: will people still care about being tracked? Or will this tracking capability be kept going in case we have another pandemic?

In the meantime, if you want privacy, keep the location setting off on your phone until you need it turned on. And maybe put your phone in airplane mode when you don’t need to be on a phone network.

Learn More

Smartphones and Tracking the Spread of COVID-19

A primer on mobile privacy and security

Viral Coronavirus Cellphone Maps Send A Powerful Message

Corona Virus tracking on your phone

Contact Tracing,to%20COVID%2D19.

Covid tracking Q&A

How contact tracing works on your phone

Using phone to track covid exposure

mobile phone tracking


  • Tim Slavin

    Tim is an award-winning writer and technologist who enjoys teaching tech to non-technical people. He has many years experience with web sites and applications in business, technical, and creative roles. He and his wife have two kids, now teenagers, who are mad about video games.

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